Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors of Otaru, Japan, where the unique Dfb climate brings varied sun exposure throughout the year. Keeping track of UV levels is essential for preventing sunburn and promoting skin health, especially during peak hours when the UV Index can soar to a high of 9 around noon. With Otaru's beautiful coastal scenery and outdoor attractions, being informed about UV risks helps ensure that everyone enjoys the sun safely. Whether you’re exploring the city’s charming streets or relaxing by the sea, awareness of the UV Index can make all the difference in protecting your skin from harmful effects.
The UV Index steadily climbs throughout the morning, peaking at 9 between 11:00 and 12:00, indicating intense sun exposure that requires caution. As the day progresses, the index begins to decline, dropping to 7 by 14:00 and further decreasing to 5 by 15:00. By late afternoon, the UV levels drop significantly, reaching 1 by 16:00 and remaining low until sunset. It's crucial to stay protected during the midday hours when the UV Index is at its highest; wearing sunscreen and protective clothing is highly recommended to enjoy safe outdoor activities!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 3 | moderate | 30 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 8 | very high | 15 min |
| 11:00 | 9 | very high | 15 min |
| 12:00 | 9 | very high | 15 min |
| 13:00 | 8 | very high | 15 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 5 | moderate | 30 min |
| 16:00 | 3 | moderate | 30 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index reflects significant seasonal changes that impact exposure risks. January and December have low UV levels (Index 2), where burn times extend to 45 minutes. As spring approaches, by March the Index rises to 5, indicating moderate exposure risk. However, from April to September, the UV Index reaches high to very high levels, peaking at 10 in August, with burn times decreasing sharply to just 15 minutes. These months—April through September—pose the highest risk for sunburn, particularly May through August when the levels are consistently very high. Visitors and residents should prioritize sun protection during these months, recommending the use of sunscreen, hats, and protective clothing, and to seek shade during peak hours to minimize UV exposure. By October and November, the UV levels drop to moderate again, allowing for safer outdoor activities.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Otaru | 2 | 3 | 5 | 7 | 9 | 9 | 9 | 10 | 8 | 5 | 3 | 2 |
| Sapporo UVI | 2 | 3 | 6 | 7 | 9 | 9 | 9 | 10 | 8 | 5 | 3 | 2 |
| Yokohama UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Tokyo UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Nagoya UVI | 4 | 6 | 8 | 10 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 3 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |